DefaultMtlsProviderFactory.java

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package com.google.auth.mtls;

import java.io.IOException;

public class DefaultMtlsProviderFactory {

  /**
   * Creates an instance of {@link MtlsProvider}. It first attempts to create an {@link
   * com.google.auth.mtls.X509Provider}. If the certificate source is unavailable, it falls back to
   * creating a {@link SecureConnectProvider}. If the secure connect provider also fails, it throws
   * a {@link com.google.auth.mtls.CertificateSourceUnavailableException}.
   *
   * <p>This is only meant to be used internally by Google Cloud libraries, and the public facing
   * methods may be changed without notice, and have no guarantee of backwards compatibility.
   *
   * @return an instance of {@link MtlsProvider}.
   * @throws com.google.auth.mtls.CertificateSourceUnavailableException if neither provider can be
   *     created.
   * @throws IOException if an I/O error occurs during provider creation.
   */
  public static MtlsProvider create() throws IOException {
    // Note: The caller should handle CertificateSourceUnavailableException gracefully, since
    // it is an expected error case. All other IOExceptions are unexpected and should be surfaced
    // up the call stack.
    MtlsProvider mtlsProvider = new X509Provider();
    if (mtlsProvider.isAvailable()) {
      return mtlsProvider;
    }
    mtlsProvider = new SecureConnectProvider();
    if (mtlsProvider.isAvailable()) {
      return mtlsProvider;
    }
    throw new CertificateSourceUnavailableException(
        "No Certificate Source is available on this device.");
  }
}